BLACKSBURG, Virginia (CNN) -- Erin Sheehan was a freshman last year when Seung-Hui Cho peeked through the door of her German class. The next hour of her life would become a struggle for survival.

Erin Sheehan played dead while the Virginia Tech shooter went on a rampage. "I still have trouble sleeping."

"The gunman entered my room. He shot my German teacher and then proceeded to shoot the students in the classroom pretty thoroughly," she said.

Sheehan was only one of four students in the room not to get shot. She jumped on the floor and remained quiet while Cho went on his rampage. "I thought if I played dead then he hopefully would think I was already hit."

She listened as the killer left her Norris Hall classroom to attack another room. She and the other survivors barricaded the door to keep Cho from coming back. "I tried to use a podium at the front of the classroom to block the door, because the gunman was shoving at the door and started firing through the door. We didn't think we were going to be able to hold it," she said. Watch Sheehan remember a day of horror »

Sheehan is now a sophomore at Virginia Tech. Like so many on campus, April 16, 2007, marks the worst day of her life, when Cho killed 32 students and professors in the deadliest school shooting in U.S. history.

Sheehan recently accompanied CNN to what is known as the Virginia Tech April 16, 2007 Prevail Archive -- an office space on the edge of campus where mementoes sent from across the world are temporarily warehoused. The university is cataloging and documenting every item it can save in order to create a permanent collection as well as an online archive that the public can access. Take a tour of the archive »

Teddy bears, an American flag from the U.S. Embassy in Afghanistan, painted eggs, the hood of a race car, condolence posters signed by Koreans and a letter from President Bush are housed there. Thousands of other letters are also kept in the archive.

"This is making me feel super bad. Because a lot of people died at Blacksburg. I love VT," wrote one young child.

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Walking through the archive for the first time, Sheehan was overcome with emotion. She stopped and held a picture of all the victims, pointing out her slain German teacher and another classmate. "I believe this is Nicole White, she sat right next to me. And I think I would credit her with taking bullets for me," she said in a muted tone. Watch letters to Virginia Tech »

Of the entire archive, she added, "I don't ever remember seeing it all together like this before. I think it is really remarkable that so many people cared to reach out to us like this."

Tamara Kennelly is the archivist at Virginia Tech. She's responsible for documenting how everyone beyond the campus dealt with the tragedy, when the world was joined by four words: "We are all Hokies."

They've received just about anything, from condolences books from funeral homes to messages from prisons to letters from elementary students.

"There are always people who really have their own story to tell or a powerful way of putting it. And when you find those letters, they stay with you -- all day, all week," said Amy Vilelle, the manuscript archivist. "There are a few that I will not ever forget reading."

Some are very personal, like a pair of goggles from a lab partner. "Mike may you rest in peace. You will forever be remembered as my favorite lab partner. We'll be missing you," it says on the goggles.

Fighting back tears, Kennelly said, "This job is very moving because you get something and you read it and you think, 'oh gosh, they want to share something with us somehow. They want to reach out and give some kindness.' "

Gail McMillan, the director of digital archives, says it's especially difficult to read material from children. "It's hard to know what kind of impact this may have on them."

Their job is not only to remember, but to preserve, an archival collection for the university. For those who lived it, the tragic events of April 16, 2007, are still too fresh to put into the past.

"I still have trouble sleeping some days," Sheehan said.

"It really does bother me because I still understand I could have been killed so easy, and there is no explanation why I wasn't."E-mail to a friend